Fig. 1: The intrinsic charm PDF and comparison with models.

Left, the purely intrinsic (3FNS) result (blue) with PDFU alone, compared to the 4FNS PDF, which includes both an intrinsic and a radiative component, at Q = mc = 1.51 GeV (orange). The purely intrinsic (3FNS) result obtained using N3LO matching is also shown (green). Right, the purely intrinsic (3FNS) final result with total uncertainty (PDFU + MHOU), with the PDFU indicated as a dark shaded band; the predictions from the original BHPS model1 and from the more recent meson/baryon cloud model5 are also shown for comparison (dotted and dot-dashed curves, respectively).